The present invention relates to silver halide emulsion, a production process thereof, and a silver halide photographic light-sensitive material and a photothermographic material each having a layer comprising the emulsion.
Silver halide as a photosensitive element of photographic light-sensitive materials can be formed to have a grain size of 0.01 xcexcm or more by appropriately designing the preparation process in a photographic gelatin. However, silver halide grains having a grain size of from 0.005 to 0.1 xcexcm undergo physical ripening with the passing of time, where small grains dissolve to grow into large grains. As a result, the grain size disadvantageously becomes large.
In order to prevent the growing of silver halide grains into large grains, a stabilizer for stabilizing the photographic performance, such as tetrazaindenes and mercaptothiazoles, has been conventionally used. However, if the stabilizer is added in an amount large enough to fix the grain size, a spectral sensitizing dye does not adsorb to the grain surface and a photographic light-sensitive material using the emulsion cannot have a desired sensitivity. Thus, it has been difficult to attain results in both the grain size and the photographic performance. In particular, silver chloride fine grain has high solubility and the physical ripening thereof is hard to prevent. If the grain size of this silver halide fine grain can be maintained, various advantages can be provided, for example, the storability of emulsion can be increased or a large number of grains can be obtained with the same silver amount.
These advantages can be applied to photothermographic materials. In the photothermographic material, the silver halide grain works as a photosensitive element and by forming the silver halide grains as fine grains, the silver amount can be reduced and thereby the storability can be improved. The photothermographic material is described below.
In the medical diagnosis field, reduction in the amount of processing waste solution is keenly demanded in recent years from the viewpoint of environmental conservation and space savings. To cope with this demand, technology is required relating to photothermographic materials for use in medical diagnosis or graphic art or other photographic use, which can be effectively exposed by a laser image setter or a laser imager and can form a sharp black image having high resolution and sharpness. These photothermographic materials can dispense with processing chemicals of solution system and afford users a more simple heat-developing system which does not impair the environment.
The same is also demanded in the field of general image-forming materials, however, the image for medical diagnosis use must be finely drawn, therefore, must have a high image quality with good sharpness and excellent graininess. Furthermore, in view of diagnostic convenience, an image of blue black image tone is preferred. At the present, various hard copy systems using a pigment or a dye are commercially available, such as ink jet printer and electrophotography, however, these are not a satisfactory output system for the image in medical use.
On the other hand, (photo)thermographic systems using a silver salt of an organic acid are described, for example, in U.S. Pat. Nos 3,152,904 and 3,457,075, D. Klosterboer, Thermally Processed Silver Systems, and J. Sturge, V. Walworth and A. Shepp (compilers), Imaging Processes and Materials, 8th ed., chapter 9th, page 279, Neblette (1989). In particular, photothermographic materials generally have a light-sensitive layer comprising a binder matrix having dispersed therein a catalytic amount of a photocatalyst (for example, silver halide), a reducing agent, a reducible silver salt (for example, a silver salt of an organic acid) and if desired, a toner for controlling the silver tone. The photothermographic material after image exposure is heated at a high temperature (for example, 80xc2x0 C. or more) to cause an oxidation-reduction reaction between the silver halide or reducible silver salt (acting as an oxidizing agent) and the reducing agent and thereby form a black silver image. The oxidation-reduction reaction is accelerated by the catalytic action of a silver halide latent image produced by the exposure. Therefore, the black silver image is formed in the exposed area. This is disclosed in a large number of publications including U.S. Pat. No. 2,910,377 and JP-B-43-4924 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d) The (photo) thermographic system using a silver salt of an organic acid can provide an image satisfied in the image quality and the tone for medical diagnosis uses.
Silver halide emulsions produced by adding a hexacyano metal complex during or after the formation of silver halide grains are described in Research Disclosure, Vol. 176, No. 17643, Item IA (1978) and Vol. 367, Item 36736 (1994), JP-A-2-20853 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and JP-A-2-20854. In these publications, a technique of incorporating (doping) a hexacyano metal complex into the inside of a silver halide grain. However, these silver halide emulsions are not yet satisfied in the sensitivity and the storability and still in need of improvements.
An object of the present invention is to provide a silver halide grain emulsion having a small grain size.
Another object of the present invention is to provide a silver halide photographic light-sensitive material having high sensitivity and excellent image preservability against light.
A still another object of the present invention is photothermographic material having high sensitivity and excellent image preservability against light.
The above-described objects can be attained by the following means.
(1) A silver halide emulsion comprising at least a dispersion medium and silver halide grains, wherein the silver halide grains have an average grain size of from 0.005 to 0.1 xcexcm and a hexacyano metal complex represented by formula (I) is present on the outermost surface of the silver halide grain:
[M(CN)6]nxe2x88x92xe2x80x83xe2x80x83(I)
wherein M represents Fe, Ru, Os, Co, Rh, Ir, Cr or Re, and n represents 3 or 4.
(2) The silver halide emulsion as described in (1) above, wherein the silver halide grain contains in the inside thereof a coordination metal complex or metal ion containing a metal belonging to the elements of Group III to Group XIV of the Periodic Table.
(3) The silver halide emulsion as described in (2) above, wherein the coordination metal complex contained in the inside of the silver halide grain is a compound represented by formula (III):
[M1(CN)6]n1xe2x88x92xe2x80x83xe2x80x83(III)
wherein M1 represents Fe, Ru, Os, Co, Rh, Ir, Cr or Re, and n1 represents 3 or 4.
(4) The silver halide emulsion as described in (2) or (3) above, wherein the coordination metal complex contained in the inside of the silver halide grain is an iridium complex.
(5) The silver halide emulsion as described in any one of (1) to (4) above, wherein the silver halide emulsion is chalcogen sensitized.
(6) The silver halide emulsion as described in any one of (1) to (5) above, wherein the silver halide grains are formed in the presence of an oxidizing agent for silver.
(7) The silver halide emulsion as described in any one of (1) to (6) above, wherein the silver halide emulsion is chemically sensitized in the presence of a spectral sensitizing dye.
(8) A method for producing a silver halide emulsion comprising silver halide grains having an average grain size of from 0.005 to 0.1 xcexcm, wherein a hexacyano metal complex represented by the following formula (I) is added after the addition of an aqueous silver nitrate solution used for the grain formation is completed but before starting the chemical sensitization process:
[M(CN)6]nxe2x88x92xe2x80x83xe2x80x83(I)
wherein M represents Fe, Ru, Os, Co, Rh, Ir, Cr or Re, and n represents 3 or 4.
(9) A silver halide light-sensitive material comprising a support having thereon at least one light-sensitive layer comprising the silver halide emulsion described in any one of (1) to (7) above.
(10) A photothermographic material comprising a support having thereon at least one light-sensitive layer containing a light-sensitive silver halide, a light-insensitive silver salt of an organic fatty acid, a reducing agent for silver ion and a binder, wherein a silver halide emulsion described in any one of (1) to (7) above is prepared independently of the silver salt of the organic fatty acid and mixed with the silver salt of the organic fatty acid at the coating and the mixture is coated and dried to form the light-sensitive layer.
The present invention is described in detail below.
In the present invention a hexacyano metal complex represented by the following formula (I) (hereinafter sometimes referred to as xe2x80x9ca hexacyano metal complex of the present inventionxe2x80x9d) is used
[M(CN)6]nxe2x88x92xe2x80x83xe2x80x83(I)
wherein M represents Fe, Ru, Os, Co, Rh, Ir, Cr or Re, and n represents 3 or 4. M is preferably Fe or Ru, more preferably Fe.
Specific examples of the compound are set forth below.
(I-1) [Fe(CN)6]4xe2x88x92
(I-2) [Fe(CN)6]3xe2x88x92
(I-3) [Ru(CN)6]4xe2x88x92
(I-4) [Os(CN)6]4xe2x88x92
(I-5) [Co(CN)6]3xe2x88x92
(I-6) [Rh(CN)6]3xe2x88x92
(I-7) [Ir(CN)6]3xe2x88x92
(I-8) [Cr(CN)6]3xe2x88x92
(I-9) [Re(CN)6]3xe2x88x92
The hexacyano metal complex of the present invention is present in the form of ion in an aqueous solution, therefore, the counter cation is not important but a cation easy to mix with water and suitable for the precipitation operation of a silver halide emulsion is preferred. Examples thereof include alkali metal ions such as sodium ion, potassium ion, rubidium ion, cesium ion and lithium ion, ammonium ions, and alkylammonium ions represented by the following formula (II):
[R1R2R3R4N]+xe2x80x83xe2x80x83(II)
wherein R1, R2, R3 and R4 each represents a substituent freely selected from alkyl groups such as a methyl group, an ethyl group, a propyl group, an iso-propyl group and an n-butyl group. Among these, compounds where R1, R2, R3 and R4 are the same are preferred, such as tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion and tetra(n-butyl)ammonium ion.
The hexacyano metal complex of the present invention may be added after mixing it with water, a mixed solvent of water and an appropriate organic solvent miscible with water (for example, alcohols, ethers, glycols, ketones, esters and amides), or gelatin.
The amount of the hexacyano metal complex of the present invention added is preferably 1xc3x9710xe2x88x925 to 1xc3x9710xe2x88x922 mol, more preferably from 1xc3x9710xe2x88x924 to 1xc3x9710xe2x88x923 mol, per mol of silver.
For allowing the hexacyano metal complex of the present invention to be present on the outermost surface of a silver halide grain, the hexacyano metal complex of the present invention is directly added after the addition of an aqueous silver nitrate solution used for the grain formation is completed but before starting the chemical sensitization process by performing chalcogen sensitization such as sulfur sensitization, selenium sensitization and tellurium sensitization or noble metal sensitization such as gold sensitization, for example, before the completion of charging process, during the water washing process, during the dispersing process or before the chemical sensitization process. In order to prevent growing of silver halide fine grains, the hexacyano metal complex is preferably added without delay after the grain formation but before the completion of charging process.
The addition of hexacyano metal complex is started after 96 wt %, preferably 98 wt %, more preferably 99 wt %, of the total amount of silver nitrate added for forming grains is added.
By the studies this time, it is found that the hexacyano metal complex added after the addition of an aqueous silver nitrate solution immediately before the completion of grain formation adsorbs to the outermost surface of a silver halide grain. Most of the complexes adsorbed form a sparingly-soluble salt with silver ion on the grain surface. The silver salt of hexacyanoferrate (II) formed is a salt more sparingly soluble than AgI, therefore, the redissolving of fine grains can be prevented and silver halide fine grains having a small grain size can be produced.
The silver halide emulsion of the present invention is a photographic silver halide emulsion comprising silver halide grains having an average grain size of from 0.005 to 0.1 xcexcm (in the present invention, sometimes referred to as a xe2x80x9csilver halide fine grain of the present inventionxe2x80x9d) When the silver halide grain is a so-called regular crystal having, for example, a cubic or octahedral form, and when it is a so-called irregular crystal having, for example, a spherical or bar form, the grain size as used herein means the diameter of an imaginary sphere having the same volume as the silver halide grain (sphere-equivalent size). When the silver halide grain is a tabular grain, the grain size means the diameter of an imaginary circle having the same area as the projected area of a main face (circle-equivalent size). In the present invention, the average grain size is preferably from 0.008 to 0.07 xcexcm, more preferably from 0.010 to 0.060 xcexcm. The grain size can be confirmed by an electron microscope.
Examples of the shape of silver halide grain include cubic form, octahedral form, tabular form, spherical form, bar form and pebble form. In the present invention, cubic grain is preferred. A silver halide grain having rounded corners may also be used. The face index (Miller indices) of the outer surface plane of a light-sensitive silver halide grain is not particularly limited, however, it is preferred that the occupation ratio of [100] faces readily causing the interaction of hexacyano metal ion and silver ion is high. The occupation ratio is preferably 50% or more, more preferably 65% or more, still more preferably 80% or more. The percentage of [100] faces according to the Miller indices can be obtained by the method described in T. Tani, J. Imaging Sci., 29, 165 (1985) using the adsorption dependency of [111] face and [100] face upon adsorption of the sensitizing dye.
The halogen composition of silver halide grains for use in the present invention is not particularly limited, and silver chloride, silver chlorobromide, silver bromide, silver iodobromide and silver iodochlorobromide may be used. The halogen composition distribution within the grain may be uniform or the halogen composition may be stepwise changed or continuously changed. A silver halide grain having a core/shell structure may also be preferably used. With respect to the structure, the core/shell grain preferably has from 2 to 5-ply structure, more preferably from 2 to 4-ply structure. Furthermore, a technique of localizing silver bromide on the surface of silver chloride or silver chlorobromide grains may also be preferably used. The emulsion of the present invention preferably has a silver iodide content of from 0 to 5 mol %.
In the present invention, a silver halide grain having a dislocation line may also be preferably used. The grain having a dislocation line is disclosed in U.S. Pat. No. 4,806,461.
In the present invention, the silver halide grain preferably contains in the inside thereof a coordination metal complex or metal ion containing a metal belonging to the elements of Groups III to XIV of the periodic table. The metal of the coordination metal complex or metal ion may be selected from the elements of Groups III to XIV in the periodic table having Group numbers of I to XVIII from the left. The metal is preferably selected from the metals belonging to the elements of Groups IV, V and VI of the periodic table, more preferably from vanadium, chromium, manganese, iron, cobalt, nickel, niobium, molybdenum, ruthenium, rhodium, palladium, tantalum, tungsten, rhenium, osmium, iridium, platinum and lead. The metal is particularly preferably an iridium complex. The metal may be used as a metal ion in the form of a metal salt such as ammonium salt, acetate, nitrate, sulfate, phosphate and hydroxide, however, by using the meal as a mononuclear coordination metal salt such as hexacoordinated complex salt or tetracoordinated complex salt, or as a polynuclear or multinuclear metal complex salt, the performance owing to the ligand or complex salt structure may be brought out. Preferred examples of the ligand include anionic ligands such as fluoride ion, chloride ion, bromide ion, iodide ion, oxide ion, sulfide ion, selenide ion, telluride ion, cyanide ion, thiocyanide ion, selenocyanide ion, tellurocyanide ion, cyanate ion, nitride ion and azide ion, neutral ligands such as water, carbonyl, nitrosyl, thionitrosyl and ammonia, and organic ligands containing one or more carbon-carbon, carbon-hydrogen or carbon-nitrogen-hydrogen bond, such as 4,4xe2x80x2-bipyridine, pyrazine and thiazole disclosed in U.S. Pat. No. 5,360,712.
Specific examples of the metal ion include those described in Comprehensive Coordination Chemistry, Pergamon Press (1987).
For the doping into a silver halide grain, the coordination metal complex or metal ion of the present invention is preferably added directly to the reaction solution during the formation of silver halide grains or added to the reaction solution for the grain formation after adding it to a solution containing halide ion for forming silver halide grains or other solution. Furthermore, various adding methods may be used in combination.
The coordination metal complex or metal ion of the present invention may be doped to uniformly reside inside the grain or as disclosed in JP-A-4-208936, JP-A-2-125245 an JP-A-3-188437, may be doped in a higher concentration in the grain surface phase. Also, as disclosed in U.S. Pat. No. 5,256,530, the grain surface phase may be modified by physically ripening it with the doped fine grains. This method of preparing doped fine grains and adding the fine grains to physically ripen and thereby dope silver halide grains is preferably used. These doping methods may also be used in combination.
The coordination metal complex or metal ion capable of satisfying the requirements in the present invention may be incorporated into a silver halide grain in the same concentration per mol of silver as conventionally used for the doping of transition metals. Concentrations over a very wide range are known and the coordination metal complex or metal ion may be used in a concentration of from a low concentration of 10xe2x88x9210 mol per mol of silver disclosed in JP-A-51-107129 to a high concentration of 10xe2x88x923 mol per mol of silver disclosed in U.S. Pat. Nos. 3,687,676 and 3,690,891. The effective concentration greatly varies depending on the amount of halide in the grain, the coordination complex or metal ion selected, the oxidation state thereof, the kind of ligand, if present, and the desired photographic effects.
The doped amount or doping ratio of the coordination metal complex or metal ion of the present invention in a silver halide grain may be determined by measuring the metal ion doped using atomic absorption method, ICP method (inductively coupled plasma spectrometry), ICPMS method (inductively coupled plasma mass spectrometry) or the like.
Among these coordination metal complexes which can be incorporated into the silver halide grain, the hexacyano metal complex represented by formula (III) is preferred:
[M1(CN)6]n1xe2x88x92xe2x80x83xe2x80x83(III)
wherein M1 represents Fe, Ru, Os, Co, Rh, Ir, Cr or Re, and n1 represents 3 or 4.
Specific examples of the compound are the same as those of the compound represented by formula (I).
The coordination metal complex or metal ion may be added after mixing it with water, a mixed solvent of water and an appropriate organic solvent miscible with water (for example, alcohols, ethers, glycols, ketones, esters and amides), or gelatin.
The coordination metal complex or metal ion is preferably added directly to the reaction solution at the formation of silver halide grains or incorporated by adding it to an aqueous halide solution for forming silver halide grains or other solution and then subjecting the solution to the grain formation. Furthermore, a method of adding the coordination metal complex or metal ion using fine grains doped with the metal ion of the present invention may be used. These adding methods may also be used in combination.
The amount of coordination metal complex or metal ion added is preferably from 1xc3x9710xe2x88x928 to 1xc3x9710xe2x88x923 mol, more preferably from 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x924 mol, per mol of silver.
With respect to the position where the coordination metal complex or metal ion is doped, the localized phase having a coordination metal complex or metal ion concentration at least 10 times higher than other parts is present in the surface phase which occupies 50% or less, preferably 30% or less, of the grain volume. The coordination metal complex or metal ion may also be doped in an epitaxial phase formed on the grain surface.
Iridium Metal
As the metal complex which can be incorporated into a silver halide grain, an iridium complex is preferably used in combination. The iridium complex includes trivalent iridium complex and tetravalent iridium complex. Examples thereof include hexachloroiridium(III) complex salt, hexachloroiridium(IV) complex salt, hexabromoiridium(III) complex salt, hexabromoiridium(IV) complex salt, hexaiodoiridium(III) complex salt, hexaiodoiridium(IV) complex salt, aquapentachloroiridium(III) complex salt, aquapentachloroiridium(IV) complex salt, aquapentabromoiridium(III) complex salt, aquapentabromoiridium(IV) complex salt, aquapentaiodoiridium(III) complex salt, aquapentaiodoiridium(IV) complex salt, diaquatetrachloroiridium(III) complex salt, diaquatetrachloroiridium(IV) complex salt, diaquatetrabromoiridium(III) complex salt, diaquatetrabromoiridium(IV) complex salt, diaquatetraiodoiridium(III) complex salt, diaquatetraiodoiridium(IV) complex salt, triaquatrichloroiridium(III) complex salt, triaquatrichloroiridium(IV) complex salt, triaquatribromoiridium(III) complex salt, triaquatribromoiridium(IV) complex salt, triaquatriiodoiridium(III) complex salt, triaquatriiodoiridium(IV) complex salt, hexammineiridium(III) complex salt and hexammineiridium(IV) complex salt, however, the present invention is by no means limited thereto.
The amount of the iridium complex added is preferably from 10xe2x88x929 to 10xe2x88x923 mol, more preferably from 10xe2x88x926 to 10xe2x88x924 mol, per mol of silver halide.
Chalcogen Sensitization
The silver halide emulsion of the present invention is preferably sensitized using sulfur sensitization, selenium sensitization or tellurium sensitization solely or using a plurality of these sensitization treatments.
The sulfur sensitization preferably used in the present invention is usually performed by adding a sulfur sensitizer and stirring the emulsion at a high temperature of 40xc2x0 C. or more for a predetermined time. The sulfur sensitizer used may be a known compound. For example, in addition to the sulfur compound contained in gelatin, various sulfur compounds such as thiosulfates, thioureas, thiazoles and rhodanines may be used. Among these, preferred are a thiosulfate and a thiourea compound. The amount of the sulfur sensitizer varies depending on various conditions such as pH, temperature and silver halide grain size at the chemical ripening, however, it is usually from 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x922 mol, preferably from 1xc3x9710xe2x88x925 to 1xc3x9710xe2x88x923 mol, per mol of silver halide.
The selenium sensitizer for use in the present invention may be a known selenium compound. The selenium sensitization is usually performed by adding a labile and/or non-labile selenium compound and stirring the emulsion at a high temperature of 40xc2x0 C. or higher for a predetermined time. Examples of the labile selenium compound which can be used include the compounds described in JP-B-44-15748, JP-B-43-13489, JP-A-4-25832, JP-A-4-109240 and JP-A-3-121798. In particular, the compounds represented by formulae (VIII) and (IX) of JP-A-4-324855 are preferred.
The tellurium sensitizer for use in the present invention is a compound of forming silver telluride presumed to become a sensitization nucleus, on the surface or in the inside of a silver halide grain. The rate of formation of silver telluride in a silver halide emulsion can be examined according to the method described in JP-A-5-313284. Examples of the tellurium sensitizer include diacyltellurides, bis(oxycarbonyl) tellurides, bis-(carbamoyl)tellurides, bis(oxycarbonyl)ditellurides, bis(carbamoyl)ditellurides, compounds having a Pxe2x95x90Te bond, tellurocarboxylates, Te-organyltellurocarboxylic acid esters, di(poly)tellurides, tellurides, telluroles, telluroacetals, tellurosulfonates, compounds having a Pxe2x80x94Te bond, Te-containing heterocyclic compounds, tellurocarbonyl compounds, inorganic tellurium compounds and colloidal tellurium. Specific examples of the tellurium sensitizer which can be used include the compounds described in U.S. Pat. Nos. 1,623,499, 3,320,069 and 3,772,031, British Patents 235,211, 1,121,496, 1,295,462 and 1,396,696, Canadian Patent 800,958, JP-A-4-204640, JP-A-3-53693, JP-A-3-131598, JP-A-4-129787, J. Chem. Soc. Chem. Commun., 635 (1980), ibid., 1102 (1979), ibid., 645 (1979), J. Chem. Soc. Perkin. Trans. 1, 2191 (1980), S. Patai (compiler), The Chemistry of Organic Selenium and Tellurium Compounds, Vol. 1 (1986), and ibid., Vol. 2 (1987). In particular, the compounds represented by formulae (II), (III) and (IV) of JP-A-5-313284 are preferred.
The used amount of the selenium or tellurium sensitizer for use in the present invention varies depending on silver halide grain used, chemical ripening conditions and the like, however, it is usually from 1xc3x9710xe2x88x928 to 1xc3x9710xe2x88x922 mol, preferably on the order of from 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x923 mol, per mol of silver halide. The conditions for chemical sensitization in the present invention are not particularly limited, however, the pH is from 5 to 8, the pAg is from 6 to 11, preferably from 7 to 10, and the temperature is from 40 to 95xc2x0 C., preferably from 45 to 85xc2x0 C.
The silver halide emulsion of the present invention may also be sensitized using a combination of chalcogen sensitization with gold sensitization or reduction sensitization. When the chalcogen sensitization is used in combination with gold sensitization, for example, a combinations of sulfur sensitization and gold sensitization, a combination of selenium sensitization and gold sensitization, a combination of sulfur sensitization, selenium sensitization and gold sensitization, a combination of sulfur sensitization, tellurium sensitization and gold sensitization, and a combination of sulfur sensitization, selenium sensitization, tellurium sensitization and gold sensitization are preferred.
Gold Sensitization
In the case of applying gold sensitization, the gold sensitizer used may have a gold oxidation number of either +1 valence or +3 valence. Gold compounds commonly used as the gold sensitizer may also be used. Representative examples thereof include chloroauric acid, potassium chloroaurate, auric trichloride, potassium auric thiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium aurothiocyanate and pyridyltrichlorogold.
The amount of the gold sensitizer added varies depending on various conditions, however, as a standard, it is from 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x923 mol, preferably from 1xc3x9710xe2x88x925 to 1xc3x9710xe2x88x924 mol, per mol of silver halide.
Reduction Sensitization
The silver halide emulsion of the present invention may be sensitized using reduction sensitization. Specific examples of the reduction sensitizer which can be used include ascorbic acid, thiourea dioxide, stannous salt, aminoiminomethanesulfinic acid, hydrazine derivatives, borane compounds, silane compounds and polyamine compounds. The reduction sensitization may also be performed by ripening the emulsion while maintaining the pH at 7 or more and the pAg at 8.3 or less. Furthermore, the reduction sensitization may be performed by introducing the single addition moiety of silver ion during the grain formation.
To the silver halide emulsion of the present invention, a thiosulfonic acid compound may be added by the method described in European Patent 293,917.
In the silver halide emulsion of the present invention, a cadmium salt, a sulfite, a lead salt or a thallium salt may be allowed to be present together during the formation or physical ripening of silver halide grains.
In the light-sensitive material of the present invention, a sole kind of silver halide emulsion may be used or two or more kinds of silver halide emulsions (for example, different in the average grain size, different in the halogen composition, different in the crystal habit or different in the conditions of chemical sensitization) may be used in combination.
Sensitizing Dye
The sensitizing dye for use in the present invention may be any as long as it can adsorb to a silver halide grain and spectrally sensitize the silver halide grain in the desired wavelength region (600 nm or more). Examples of the sensitizing dye which can be used include a cyanine dye, a merocyanine dye, a complex cyanine dye, a complex merocyanine dye, a holopolar cyanine dye, a styryl dye, a hemicyanine dye, an oxonol dye and a hemioxonol dye. Useful sensitizing dyes for use in the present invention are described, for example, in Research Disclosure, Item 17643 IV-A, page 23 (December, 1978), ibid., Item 1831 X, page 437 (August, 1979), and publications cited therein. In particular, sensitizing dyes having spectral sensitivity suitable for spectral characteristics of the light source in various laser imagers, scanners, image setters and photomechanical cameras can be advantageously selected.
For the red light source in the spectral sensitization to red light, such as Hexe2x80x94Ne laser, red semiconductor laser and LED, the sensitizing dye may be advantageously selected from Compounds I-1 to I-38 of JP-A-54-18726, Compounds I-1 to I-35 of JP-A-6-75322, Compounds I-1 to I-34 of JP-A-7-287338, Dyes 1 to 20 of JP-B-55-39818, Compounds I-1 to I-37 of JP-A-62-284343, and Compounds I-1 to I-34 of JP-A-7-287338.
For the semiconductor laser light source in the wavelength region of from 750 to 1,400 nm, various known dyes including cyanine, merocyanine, styryl, hemicyanine, oxonol, hemioxonol and xanthene dyes may be used and by these dyes, the emulsion can be spectrally sensitized in an advantageous manner. Useful cyanine dyes are cyanine dyes having a basic nucleus such as thiazoline nucleus, oxazoline nucleus, pyrroline nucleus, pyridine nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus and imidazole nucleus. Preferred examples of useful merocyanine dyes include, in addition to those having the above-described basic nucleus, dyes having an acidic nucleus such as thiohydantoin nucleus, rhodanine nucleus, oxazolidine-dione nucleus, thiazolinedione nucleus, barbituric acid nucleus, thiazolinone nucleus, malononitrile nucleus and pyrazolone nucleus. Among these cyanine and merocyanine dyes, those having an imino group or a carboxyl group are particularly effective. The sensitizing dye may be appropriately selected from known dyes described, for example, in U.S. Pat. Nos. 3,761,279, 3,719,495 and 3,877,943, British Patents 1,466,201, 1,469,117 and 1,422,057, JP-B-3-10391, JP-B-6-52387, JP-A-5-341432, JP-A-6-194781 and JP-A-6-301141.
Particularly preferred examples of the structure of the dye for use in the present invention include cyanine dyes having a thioether bond-containing substituent group (for example, dyes described in JP-A-62-58239, JP-A-3-138638, JP-A-3-138642, JP-A-4-255840, JP-A-5-72659, JP-A-5-72661, JP-A-6-222491, JP-A-2-230506, JP-A-6-258757, JP-A-6-317868, JP-A-6-324425, Japanese Published Unexamined International Application 7-500926 and U.S. Pat. No. 5,541,054), dyes having a carboxylic acid group (for example, dyes described in JP-A-3-163440, JP-A-6-301141 and U.S. Pat. No. 5,441,899), merocyanine dyes, polynuclear merocyanine dyes and polynuclear cyanine dyes (for example, dyes described in JP-A-47-6329, JP-A-49-105524, JP-A-51-127719, JP-A-52-80829, JP-A-54-61517, JP-A-59-214846, JP-A-60-6750, JP-A-63-159841, JP-A-6-35109, JP-A-6-59381, JP-A-7-146537, Japanese Published Unexamined International Application 55-50111, British Patent 1,467,638 and U.S. Pat. No. 5,281,515).
Also, dyes capable of forming J-band disclosed in U.S. Pat. Nos. 5,510,236 and 3,871,887 (dye described in Example 5), JP-A-2-96131 and JP-A-59-48753 may be preferably used in the present invention.
In the present invention, merocyanine dyes which have been heretofore scarcely used in the addition prior to chemical sensitization because of their weak adsorption are particularly preferred.
These sensitizing dyes may be used individually or in combination of two or more thereof. In particular, the combination of sensitizing dyes is often used for the purpose of supersensitization. In combination with the sensitizing dye, a dye which itself has no spectral sensitization effect or a material which absorbs substantially no visible light, but which exhibits supersensitization may be contained in the emulsion. Useful sensitizing dyes, combinations of dyes which exhibit supersensitization, and materials which exhibit supersensitization are described in Research Disclosure, Vol. 176, 17643, page 23, Item IV-J (December, 1978), JP-B-49-25500, JP-B-43-4933, JP-A-59-19032 and JP-A-59-192242.
For adding the sensitizing dye to a silver halide emulsion, the dye may be directly dispersed in the silver halide emulsion or may be added to the emulsion after dissolving it in a sole or mixed solvent of water, methanol, ethanol, propanol, acetone, methyl cellosolve, 2,2,3,3-tetrafluoropropanol, 2,2,2-trifluoroethanol, 3-methoxy-1-propanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol or N,N-dimethylformamide.
Also, the sensitizing dye may be added to the emulsion by a method described in U.S. Pat. No. 3,469,987 where a dye is dissolved in a volatile organic solvent, the solution is dispersed in water or a hydrophilic colloid and the dispersion is added to the emulsion, a method described in JP-B-44-23389, JP-B-44-27555 and JP-B-57-22091 where a dye is dissolved in an acid and the solution is added to the emulsion or formed into an aqueous solution in the presence of,an acid or a base together and then added to the emulsion, a method described in U.S. Pat. Nos. 3,822,135 and 4,006,025 where a dye is formed into an aqueous solution or a colloid dispersion in the presence of a surface active agent together and the aqueous solution or dispersion is added to the emulsion, a method described in JP-A-53-102733 and JP-A-58-105141 where a dye is directly dispersed in a hydrophilic colloid and the dispersion is added to the emulsion, or a method described in JP-A-51-74624 where a dye is dissolved using a compound capable of red-shift and the solution is added to the emulsion. Ultrasonic waves may also be used in the solution.
The sensitizing dye for use in the present invention may be added to a silver halide emulsion of the present invention in any process known to be useful during the preparation of emulsion. For example, the dye may be added in the period during the formation of silver halide grains and/or before desalting or in the period during desalting and/or after desalting but before initiation of the chemical ripening as disclosed in U.S. Pat. Nos. 2,735,766, 3,628,960, 4,183,756 and 4,225,666, JP-A-58-184142 and JP-A-60-196749, or the dye may be added in any period or any process if it is before the coating of the emulsion, such as in the period immediately before or during chemical ripening and in the period after chemical ripening but before coating as described in JP-A-58-113920. Also, a sole kind of compound alone or compounds different in the structure in combination may be added in parts, for example, one part during the grain formation and the remaining during the chemical ripening or after the completion of chemical ripening, or one part before or during the chemical ripening and the remaining after the completion of chemical ripening as disclosed in U.S. Pat. No. 4,225,666 and JP-A-58-7629. The kind of compounds added in parts or the kind of the combination of compounds may be changed.
As such, various adding methods may be used, however, the sensitizing dye must be added to be present at the chemical sensitization.
The sensitizing dye for use in the present invention may be used in a desired amount according to the performance such as sensitivity and fogging, however, the amount used is preferably from 10xe2x88x926 to 1 mol, more preferably from 10xe2x88x924 to 10xe2x88x921 mol, per mol of silver halide in the light-sensitive layer.
The silver halide emulsion of the present invention may be further protected against production of additional fogging or stabilized against reduction in the sensitivity during stock storage, by an antifoggant, a stabilizer or a stabilizer precursor. Examples of suitable antifoggants, stabilizers and stabilizer precursors which can be used individually or in combination, include those described in JP-A-10-62899 (paragraph 0070) and Unexamined European Patent Publication No. 0803764A1 (page 20, line 57 to page 21, line 7).
The antifoggant preferably used in the present invention is an organic halide and examples thereof include the compounds disclosed in JP-A-50-119624, JP-A-50-120328, JP-A-51-121332, JP-A-54-58022, JP-A-56-70543, JP-A-56-99335, JP-A-59-90842, JP-A-61-129642, JP-A-62-129845, JP-A-6-208191, JP-A-7-5621, JP-A-7-2781, JP-A-8-15809, U.S. Pat. Nos. 5,340,712, 5,369,000 and 5,464,737.
The antifoggant for use in the present invention may be added by any method such as solution, powder or solid fine particle dispersion. The solid fine particle dispersion is prepared by a known pulverizing means (for example, ball mill, vibrating ball mill, sand mill, colloidal mill, jet mill and roller mill). In dispersing the antifoggant into solid fine particles, a dispersing aid may be used.
Although not necessary for practicing the present invention, it is sometimes advantageous to add mercury (II) salt to the emulsion layer as the antifoggant. The mercury(II) salt preferred to this purpose is mercury acetate or mercury bromide. The added amount of mercury for use in the present invention is preferably from 1xc3x9710xe2x88x929 to 1xc3x9710xe2x88x923 mol, more preferably from 1xc3x9710xe2x88x929 to 1xc3x9710xe2x88x924 mol, per mol of silver coated.
The silver halide grain for use in the present invention is formed by reacting an aqueous silver salt solution (for example, aqueous silver nitrate solution) and an aqueous halogen salt solution (for example, potassium bromide) in an aqueous colloidal solution in a reaction vessel. For performing this reaction, a single jet method where a protective colloid dispersion medium such as gelatin and an aqueous halogen salt solution are charged into a reaction vessel and an aqueous silver salt solution is added thereto while stirring over a certain period of time, and a double jet method where an aqueous gelatin solution is charged into a reaction vessel and an aqueous halogen salt solution and an aqueous silver salt solution each is added thereto over a certain period of time are known. In the present invention, the double jet method is preferred. By using the double jet method, silver halide grains having a narrow grain size distribution can be obtained.
Gelatin is advantageously used as a dispersion medium (binder or protective colloid) which can be used in the silver halide emulsion of the present invention, however, other hydrophilic colloids may also be used. Examples thereof include proteins such as gelatin derivatives, graft polymers of gelatin to other polymer, albumin and casein; cellulose derivatives such as hydroxyethyl cellulose, carboxymethyl cellulose and cellulose sulfate; saccharide derivatives such as sodium arginate and starch derivative; and various synthetic hydrophilic polymer materials such as homopolymers and copolymers of polyvinyl alcohol, polyvinyl alcohol partial acetal, poly-N-vinylpyrrolidone, poly-acrylic acid, polymethacrylic acid, polyacrylamide, polyvinyl imidazole or polyvinyl pyrazole.
As the gelatin, in addition to the general-purpose lime-processed gelatin, an acid-processed gelatin, an enzyme-processed gelatin described in Bull. Soc. Photo. Japan, Vol. 16, 30 (1966) or a gelatin hydrolysate may be used. Also, a gelatin a methionine moiety of which is subjected to oxidation processing with hydrogen peroxide may be preferably used.
The silver halide grain of the present invention is preferably desalted after the grain formation so as to adjust the pH, pAg or concentration of the dispersion medium such as gelatin.
With respect to the desalting method, the silver halide grain is preferably desalt-water washed by any conventionally known method and then dispersed in a newly prepared protective colloid. The water washing temperature may be selected according to the purpose, however, it is preferably selected within the range of from 5 to 50xc2x0 C. The desalt-water washing method may be selected from noodle water washing, dialysis using a semipermeable membrane, centrifugation, coagulation precipitation, and ion exchange. In the case of coagulation precipitation, the method may be selected from a method of using a sulfate, a method of using an organic solvent, a method of using a water-soluble polymer and a method of using a gelatin derivative. The pH at the dispersion may also be selected according to the purpose, however, it is preferably selected within the range of from 2 to 10, more preferably from 4 to 7. The pAg at the dispersion may also be selected according to the purpose, however, it is preferably selected within the range of from 6 to 10, more preferably from 7 to 9.
It may be useful in some cases to add a chalcogenide compound described in U.S. Pat. No. 3,772,031 during the preparation of emulsion. Other than S, Se and Te, a cyanate, a thiocyanate, selenocyanate, a carbonate, a phosphate or an acetate may be allowed to be present.
The silver halide photographic emulsion of the present invention may contain a mercaptoheterocyclic compound or a tetrazaindene compound described in JP-A-7-225445 so as to prevent fogging during the production process, storing or photographic processing of the light-sensitive material, or to stabilize the photographic performance. In addition to these, a large number of compounds known as an antifoggant or stabilizer may be added, such as azoles (e.g., benzothiazolium salts, nitroimidazoles, nitrobenzimidazoles, chlorobenzimidazoles, bromobenzimidazoles, mercaptothiazoles, mercaptobenzothiazoles, mercpatobenzimidazoles, mecaptothiadiazoles, aminotriazoles, benzotriazoles, nitrobenzotriazoles), azaindenes (e.g., triazaindenes, pentazaindenes), benzenethiosulfonic acids, benzenethiosulfinic acids and benzenesulfonic acid amides.
For the purpose of elevating the sensitivity or preventing fogging, the photothermographic material of the present invention may further contain an azolium salt or a benzoic acid. Examples of the azolium salt include the compounds represented by formula (XI) of JP-A-59-193447, the compounds described in JP-B-55-12581, and the compounds represented by formula (II) of JP-A-60-153039. The benzoic acids may be any benzoic acid derivative, however, preferred examples of the structure include the compounds described in U.S. Pat. Nos. 4,784,939 and 4,152,160, and JP-A-9-329865, JP-A-9-329864 and JP-A-9-281637. The azolium salt or benzoic acid may be added to any site of the light-sensitive material, however, is preferably added to a layer on the surface having a light-sensitive layer, more preferably to a layer containing a silver salt of an organic acid. The azolium salt or benzoic acid may be added at any process during the preparation of the coating solution. In the case of adding the azolium salt or benzoic acid to a silver halide emulsion layer, it may be added at any stage between the preparation of the silver halide emulsion and the preparation of the coating solution, however, is preferably added after the preparation of the silver halide emulsion but immediately before the coating. The azolium salt or benzoic acid may be added by any method such as powder, solution or fine particle dispersion and may also be added as a mixture solution with other additives such as sensitizing dye, reducing dye and toning agent. In the present invention, the amount of the azolium salt or benzoic acid may be any amount, however, it is preferably from 1xc3x9710xe2x88x926 to 2 mol, more preferably from 1xc3x9710xe2x88x923 to 0.5 mol, per mol of silver.
In the present invention, a mercapto compound, a disulfide compound or a thione compound may be contained so as to control the development by inhibiting or accelerating the development, improve the spectral sensitization efficiency or improve the storability before or after the development.